/*
 * Copyright (c) 2009 Piotr Piastucki
 * 
 * This file is part of Patchca CAPTCHA library.
 * 
 *  Patchca is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *  
 *  Patchca is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *  
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with Patchca. If not, see <http://www.gnu.org/licenses/>.
 */
package cn.dreampie.captcha.filter.library;

public class PerlinNoise {

  static int p[] = {151, 160, 137, 91, 90, 15,
      131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69,
      142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234, 75, 0,
      26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88,
      237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165,
      71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122,
      60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102,
      143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208,
      89, 18, 169, 200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109,
      198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123, 5, 202, 38, 147,
      118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182,
      189, 28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163,
      70, 221, 153, 101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98,
      108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
      251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51,
      145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199, 106, 157,
      184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236,
      205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215,
      61, 156, 180, 151, 160, 137, 91, 90, 15,
      131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69,
      142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234, 75, 0,
      26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88,
      237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165,
      71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122,
      60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102,
      143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208,
      89, 18, 169, 200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109,
      198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123, 5, 202, 38, 147,
      118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182,
      189, 28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163,
      70, 221, 153, 101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98,
      108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
      251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51,
      145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199, 106, 157,
      184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236,
      205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215,
      61, 156, 180};

  public static double noise2D(double x, double y) {
    double fx = Math.floor(x);
    double fy = Math.floor(y);
    double u, v;
    int ix = ((int) fx) & 0xFF;
    int iy = ((int) fy) & 0xFF;
    x -= fx;
    y -= fy;
    int i = p[ix];
    int j = p[ix + 1];
    u = fade(x);
    v = fade(y);
    double grad1 = grad(p[i + iy], x, y);
    double grad2 = grad(p[j + iy], x - 1, y);
    double grad3 = grad(p[i + iy + 1], x, y - 1);
    double grad4 = grad(p[j + iy + 1], x - 1, y - 1);
    return lerp(v, lerp(u, grad1, grad2), lerp(u, grad3, grad4));
  }

  static double fade(double t) {
    return t * t * t * (t * (t * 6 - 15) + 10);
  }

  static double grad(int hash, double x, double y) {
    int h = hash & 3;
    double u = (h & 1) == 0 ? x : -x;
    double v = (h & 2) == 0 ? y : -y;
    return u + v;
  }

  public static double lerp(double t, double a, double b) {
    return a + t * (b - a);
  }

}
